The Escherichia coli Subtilase Cytotoxin A Subunit Specifically Cleaves Cell-surface GRP78 Protein and Abolishes COOH-terminal-dependent Signaling

Ray, Rupa; Ridder, Gustaaf G. de; Eu, Jerry P.; Paton, Adrienne W.; Paton, James C.; Pizzo, Salvatore V.

doi:10.1074/jbc.m112.399808

Cited by 22 publications

(27 citation statements)

References 45 publications

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“…Of note, using a lactate dehydrogenase assay, we did not detect any apoptosis in MCs treated with either antibody (data not shown). The enzyme SubA is a cellimpermeable proteinase that selectively cleaves the C terminus of cell surface GRP78, whereas the SubA A272 mutant lacks proteinase activity and serves as a control for the active enzyme (27). In line with our previous results, SubA, but not the mutant form, attenuated HG-induced FAK and Akt activation ( Fig.…”

Section: Cell Surface Grp78 Is Required For Activation Of Fak and Aktsupporting

confidence: 90%

Cell surface expression of 78-kDa glucose-regulated protein (GRP78) mediates diabetic nephropathy

Krieken

Mehta

Wang

et al. 2019

Journal of Biological Chemistry

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The 78-kDa glucose-regulated protein (GRP78) is a well-established endoplasmic reticulum (ER)-resident chaperone that maintains protein homeostasis and regulates the unfolded protein response. Under conditions of ER stress, GRP78 is also expressed at the cell surface and implicated in tumorigenesis, immunity, and cellular signaling events. The role of cell surfaceassociated GRP78 (csGRP78) in the pathogenesis of diabetic nephropathy has not yet been defined. Here we explored the role of csGRP78 in regulating high glucose (HG)-induced profibrotic AKT Ser/Thr kinase (AKT) signaling and up-regulation of extracellular matrix proteins. Using primary kidney mesangial cells, we show that HG treatment, but not the osmotic control mannitol, induces csGRP78 expression through an ER stress-dependent mechanism. We found that csGRP78, known to be located on the outer membrane leaflet, interacts with the transmembrane protein integrin ␤1 and activates focal adhesion kinase and downstream PI3K/AKT signaling. Localization of GRP78 at the cell surface and its interaction with integrin ␤1 were also required for extracellular matrix protein synthesis in response to HG. Surprisingly, both the N and C termini of csGRP78 were necessary for this profibrotic response. Increased localization of GRP78 at the plasma membrane was also found in the glomerular mesangial area of type 1 diabetic mice in two different models (streptozotocin-induced and Akita). In freshly isolated glomeruli from Akita mice, csGRP78 colocalized with the mesangial cell surface marker ␣8-integrin. In conclusion, our work reveals a role for csGRP78 in HG-induced profibrotic responses in mesangial cells, informing a potential approach to treating diabetic nephropathy. Diabetic nephropathy (DN) 3 is a major complication of diabetes and the leading cause of kidney failure in North America.

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Section: Cell Surface Grp78 Is Required For Activation Of Fak and Aktsupporting

confidence: 90%

Cell surface expression of 78-kDa glucose-regulated protein (GRP78) mediates diabetic nephropathy

Krieken

Mehta

Wang

et al. 2019

Journal of Biological Chemistry

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“…1E). By staining for the C terminus of GRP78, which is surface-exposed upon translocation to the cell membrane (21), we found that TERS CM provided a progressive translocation of surface GRP78 (sGRP78) that began on day 3 and persisted through day 5 (Fig. 1F).…”

Section: Resultsmentioning

confidence: 99%

Intercellular transmission of the unfolded protein response promotes survival and drug resistance in cancer cells

et al. 2017

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Increased protein translation in cells and various factors in the tumor microenvironment can induce endoplasmic reticulum (ER) stress, which initiates the unfolded protein response (UPR). We have previously reported that factors released from cancer cells mounting a UPR induce a de novo UPR in bone marrow–derived myeloid cells, macrophages, and dendritic cells that facilitates protumorigenic characteristics in culture and tumor growth in vivo. We investigated whether this intercellular signaling, which we have termed transmissible ER stress (TERS), also operates between cancer cells and what its functional consequences were within the tumor. We found that TERS signaling induced a UPR in recipient human prostate cancer cells that included the cell surface expression of the chaperone GRP78. TERS also activated Wnt signaling in recipient cancer cells and enhanced resistance to nutrient starvation and common chemotherapies such as the proteasome inhibitor bortezomib and the microtubule inhibitor paclitaxel. TERS-induced activation of Wnt signaling required the UPR kinase and endonuclease IRE1. However, TERS-induced enhancement of cell survival was predominantly mediated by the UPR kinase PERK and a reduction in the abundance of the transcription factor ATF4, which prevented the activation of the transcription factor CHOP and, consequently, the induction of apoptosis. When implanted in mice, TERS-primed cancer cells gave rise to faster growing tumors than did vehicle-primed cancer cells. Collectively, our data demonstrate that TERS is a mechanism of intercellular communication through which tumor cells can adapt to stressful environments.

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“…The discovery that GRP78 can also localize to the cell surface under pathophysiologic conditions such as cancer, opens up new mechanisms whereby this protein may exert its pro-proliferative and anti-apoptotic function in cancer. Cellular proteins such as MTJ-1 and Par-4 have been reported to facilitate trafficking of GRP78 from the ER to the cell surface [29] , [45] ; however, their association with sGRP78 is context dependent [46] . Our studies on sGRP78 in model cell systems and in cancer cell lines studies uncovered several novel observations.…”

Section: Discussionmentioning

confidence: 99%

Cancer Cells Resistant to Therapy Promote Cell Surface Relocalization of GRP78 Which Complexes with PI3K and Enhances PI(3,4,5)P3 Production

et al. 2013

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Traditionally, GRP78 has been regarded as an endoplasmic reticulum (ER) lumenal protein due to its carboxyl KDEL retention motif. Recently, a subfraction of GRP78 is found to localize to the surface of specific cell types, serving as co-receptors and regulating signaling. However, the physiological relevance of cell surface GRP78 (sGRP78) expression in cancer and its functional interactions at the cell surface are just emerging. In this report, we combined biochemical, imaging and mutational approaches to address these issues. For detection of sGRP78, we utilized a mouse monoclonal antibody highly potent and specific for GRP78 or epitope-tagged GRP78, coupled with imaging and biochemical techniques that allowed detection of sGRP78 but not intracellular GRP78. Our studies revealed that breast and prostate cancer cells resistant to hormonal therapy actively promote GRP78 to the cell surface, which can be further elevated by a variety of ER stress-inducing conditions. We showed that sGRP78 forms complex with PI3K, and overexpression of sGRP78 promotes PIP3 formation, indicative of PI3K activation. We further discovered that an insertion mutant of GRP78 at its N-terminus domain, while retaining stable expression and the ability to translocate to the cell surface as the wild-type protein, exhibited reduced complex formation with p85 and production of PIP3. Thus, our studies provide a mechanistic explanation for the regulation of the PI3K/AKT signaling by sGRP78. Our findings suggest that targeting sGRP78 may suppress therapeutic resistance in cancer cells and offer a novel strategy to suppress PI3K activity.

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The Escherichia coli Subtilase Cytotoxin A Subunit Specifically Cleaves Cell-surface GRP78 Protein and Abolishes COOH-terminal-dependent Signaling

Cited by 22 publications

References 45 publications

Cell surface expression of 78-kDa glucose-regulated protein (GRP78) mediates diabetic nephropathy

Cell surface expression of 78-kDa glucose-regulated protein (GRP78) mediates diabetic nephropathy

Intercellular transmission of the unfolded protein response promotes survival and drug resistance in cancer cells

Cancer Cells Resistant to Therapy Promote Cell Surface Relocalization of GRP78 Which Complexes with PI3K and Enhances PI(3,4,5)P3 Production

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